This invention relates to a composite building module comprising cured concrete, prestressed metal wires and discrete foam members.
Prior to the present invention, foam materials have been incorporated within a cement composition with the object of forming light weight cement-based building modules which retain desired strength. The foam material has been incorporated as a continuous layer or as a block within a cement matrix in order to render the resultant composite more lightweight and, more resistant to water permeation through the resultant composite structure. Examples of such composites are shown for example, in U.S. Pat. Nos. 3,943,676 and 4,186,536. A significant disadvantage of these structures is that the low density foam is concentrated within a continuous portion of the volume of the composite rather than being distributed throughout the cement matrix. This results in a composite having relatively low mechanical strength within a significant portion of the composite volume caused by the low mechanical strength at the foam-cement interface. When failure occurs at a portion of this interface, the failure can easily extend along a significant portion of the interface area which can cause failure of the entire composite.
Attempts to directly mix liquid cement and discrete particles of polymeric foam have not been successful since it is difficult to wet the particle surfaces, and, as a result they tend to migrate at or near the cement matrix surface. Thus, prior to the invention, a relatively homogenous matrix of cement and foam material has not been available.
It would be desireable to provide cement-foam composites wherein position of the foam portion can be easily controlled and wherein the foam portion is homogeneously distributed throughout the cement matrix. In addition, it would be desireable to provide such composites wherein the homogeneity of foam distribution is maintained when utilizing means for prestressing the concrete-foam composite.